1. Field of the Invention
The present invention relates generally to image recording apparatus and, more particularly, to an image recording apparatus capable of effecting both still-image recording and motion-image recording.
2. Description of the Related Art
One-piece camera/VTRs (camcorders) are widely used as one type of image recording and reproducing apparatus. The constructions of recording and reproducing systems generally incorporated in such an apparatus are shown in FIGS. 1 and 2, respectively.
Referring first to FIG. 1, an imaging circuit 10 constituted by a pickup tube or a solid-state imaging device and associated circuits is driven by clock signals generated by a clock generating circuit 12 to output R, G and B signals. A matrix circuit 14 generates a luminance signal Y (=0.3R+0.59G+0.11B) and two color-difference signals (R-Y) and (B-Y) from the R, G and B signals. The luminance signal Y is frequency-modulated in a frequency modulator 16. The color-difference signals (R-Y) and (B-Y) are respectively limited to a bandwidth of 0 to about 500 kHz by low-pass filters (LPFs) 18 and 19. A quadrature two phase modulator 20 effects quadrature two phase modulation of the outputs of the LPFs 18 and 19 by using a low-index carrier wave (629 kHz in the VHS system) supplied from the clock generating circuit 12 and a signal which is 90.degree. phase-shifted with respect to the low-index carrier wave by a phase-shifting circuit 22.
A mixer 24 effects the frequency multiplexing of the frequency-modulated luminance signal Y and the low-index carrier chrominance signal received from the quadrature two phase modulator 20. A switch 26 is switched over at intervals of the reciprocal of a field frequency (for example, every 1/60 seconds in the NTSC system). Therefore, the output of the mixer 24 is applied alternately at intervals of one field to a recording/reproducing magnetic head 29A through a recording amplifier 28A or a recording/reproducing magnetic head 29B through a recording amplifier 28B, and is recorded on a magnetic tape 30.
The signals recorded on the magnetic tape 30 are reproduced by the reproducing system shown in FIG. 2. A signal reproduced by the magnetic head 29A is supplied through a reproducing amplifier 31A to one contact of a switch 32, while a signal reproduced by the magnetic head 29B is supplied through a reproducing amplifier 31B to the other contact of the switch 32. The switch 32 is switched over alternately at intervals of 1/60 seconds, similarly to the switch 26 of the recording system. A frequency-modulated luminance signal component transmitted through a high-pass filter (HPF) 33 is demodulated into the original baseband signal by a frequency demodulator 34. A low-index carrier chrominance signal component is transmitted through an LPF 35 and, in turn, is converted into a carrier chrominance signal of a 3.58-MHz carrier frequency by a frequency converter 36. A synchronizing signal separating circuit 38 separates a horizontal synchronizing signal from the reproduced signal, and a burst separating circuit 39 separates a color burst signal from the output signals of the frequency converter 36. An AFC/APC circuit 40 receives the horizontal synchronizing signal from the synchronizing signal separating circuit 38 and the color burst signal from the burst separating circuit 39, and forms a clock signal which follows time-base variations in the reproduced output, and then supplies the clock signal to the frequency converter 36 as a carrier wave.
A mixer 41 mixes the output of the frequency demodulator 34 with the output of the frequency converter 36 to provide the mixed signal at an output terminal 42.
In recent years, VTRs of a type known as "high-band .beta." or "S-VHS" have achieved high-resolution images by enhancing a carrier frequency used in frequency-modulating a luminance signal. In combination with the increased-density arrangement of imaging devices, such improvement has recently made it possible to record and reproduce images which are not inferior in quality to still images obtained with still video cameras.
As one-piece camera/VTRs (camcorders) have been widely used, the amusement value of video imaging has received wide recognition, and a number of consumers have recently been desirous not only of recording and reproducing a scene as a motion image but also of recording and reproducing a portion of the motion image as a still image.
Current VTRs usually include a "still reproduction" mode in which a desired portion of a motion image can be substantially stopped to provide observation of the corresponding still image. However, since a capstan motor must be stopped while shifting from normal reproduction to still reproduction, the quality of the reproduced still image deteriorates to some extent. In addition, since exact tracing is difficult to achieve owing to differences in the inclination of the scanning locus of a video head in successive scanning operations, a drop in S/N ratio occurs at the top and bottom of an image screen. These problems have made it impossible for consumers to view high-quality still images.
To overcome the above-described problems, the present applicant previously proposed in U.S. patent application Ser. No. 937,872 an apparatus arranged to form a still-image recording area separate from a motion-image recording area on an identical recording medium so that the period required for PCM still image information to be recorded On the still-image recording area is several seconds per frame.
In accordance with the above proposal, it is possible to provide an apparatus which can handle both motion images and still images as well as record and reproduce extremely-high-quality still images. However, the apparatus according to this proposal requires separate formation of a motion-image recording area and a still-picture recording area and hence separate arrangement of signal processing circuits for these areas. For this reason, it is difficult to avoid the problem that the size of the apparatus is relatively large.
It is to be noted that the related art of the present invention is disclosed in U.S. Pat. No. 4,415,937.